This invention relates generally to gas turbine engine variable vanes and, more particularly, to variable geometry systems used to position gas turbine engine variable vanes.
At least some known gas turbine engines include a constant volume high pressure compressor including a plurality of stationary vanes, a plurality of rotating airfoils, and a variable geometry system. The variable geometry system adjusts a position of the stationary vanes relative to a compressor flowpath. More specifically, the variable geometry system positions the variable vanes such that air flowing through the stationary vanes is re-directed towards the rotating airfoils. Re-directing the airflow facilitates improving turbine performance while maintaining aerodynamic loading within mechanical limits of the airfoils. Additionally, variable vanes facilitate the gas turbine engine to achieve efficiency and stall margin requirements.
Known variable geometry systems include an outer bellcrank, an inner bellcrank, an actuator, a master lever, a plurality of links, and an aft mount. The actuator is coupled to the outer bellcrank and positions the outer bellcrank to schedule the variable vanes. The inner bellcrank is coupled to the outer bellcrank and thus rotates proportionally with the outer bellcrank. The master lever is coupled between the inner bellcrank and the aft mount with a spherical bearing, and the links are coupled between the master lever and the variable vanes. The aft mount is coupled to the engine with at least two spherical bearings, and to the master lever with an additional bearing.
During operation of the variable geometry system, the outer bellcrank rotates and translates linear motion induced by the actuator to an angular displacement. The inner bellcrank rotates proportionally with the outer bellcrank and translates the angular displacement to linear displacements at the master lever and the links. As the inner bellcrank rotates, the master lever shifts, and a distance between a trailing edge of the master lever and the inner bellcrank is reduced. Because the aft mount is coupled to the master lever trailing edge with a spherical bearing, and because the aft mount is coupled to the engine with at least two spherical bearings, as the master lever shifts, an angular displacement is induced on the aft mount.
Over time, continued activation of the variable geometry system may induce high stresses on the aft mount bearings. More specifically, continued activation of the variable geometry system may cause excessive wear to occur between the aft mount bearing and the master lever, and between the aft mount and the engine.
In an exemplary embodiment, a gas turbine engine includes a variable geometry system aft mount that facilitates extending a useful life of the variable geometry system. The engine includes a high pressure compressor including a plurality of variable vanes and rotating vanes or airfoils. The variable geometry system is coupled to an actuator and includes a master lever, an aft mount, and a slot and groove joint. The master lever is coupled to the aft mount system with the slot and groove joint, and is configured to adjust a position of the variable vanes.
During activation of the variable geometry system, the master lever responds to movement of the actuator. As the master lever shifts forward in response to the actuator movement, the slot and groove joint restricts the movement of the master lever to two-dimensional planar movement and eliminates angular displacement stresses induced on the aft mount. Because the aft mount is prevented from being angularly displaced, the aft mount is fixedly attached to the gas turbine engine without the use of spherical bearings. Furthermore, the slot and groove joint facilitates the reduction of wear between the aft mount and the master lever.